When Stats Don’t Match Up

Novak Djokovic and Roger Federer combined to hit 70 unforced errors during the championship match at the ATP World Tour Finals. The scoreboard counted 81 errors.

Too many tennis tournaments don’t keep enough stats. The ATP World Tour Finals may have gone too far in the other direction.

At the conclusion of each singles match at the season finale in London, which ended Monday, the arena scoreboard displayed stats such as the number of total winners and unforced errors by each player or doubles team, as well as forehand and backhand winners. These were provided by the stats company IDS, which also works at several of the Grand Slam tournaments. The same stats, provided by the sports-services company MSL Technology, also were used in the television feed and projected on a screen in the media center, so that journalists could include them in their coverage of the tournament. Or at least the same categories of stats were shown. The winners and unforced-errors totals between the two sources rarely agreed, because two different stats trackers were keeping score, and coming up with different numbers.

After noticing some differences, I jotted down the numbers provided by each of the stats companies for a few matches at the tournament, including both singles semifinals. The MSL logger tended to see more unforced errors from the same match — 12.4% more in the matches I logged. MSL also reported more winners — 5.3% more — but assigns fewer of these to the forehand or backhand wings: 1.4% fewer forehand winners and 14.3% fewer for backhand winners. And MSL also counted 20% fewer net points played and won.

Some of the differences wash out because occasionally one provider will be higher on one stat, and sometimes the other. Per set the absolute difference averaged nearly one winner, more than one unforced error, 0.4 forehand winners and 0.2 backhand winners. Per match, the difference in net points won and net points played averaged 2.5 and 3.25, respectively. Overall, 58% of the 76 readings for which I had numbers from both providers differed.

Since there were already multiple stat keepers working the matches, I decided a third opinion couldn’t hurt and joined the fray for Monday’s final, won by Novak Djokovic over Roger Federer, 7-6(6), 7-5. I agreed closely with the IDS scorekeepers on winners and unforced errors, counting one fewer winner and two more unforced errors for Federer than they did and three fewer winners and one more unforced error for Djokovic. MSL was much kinder to both players, assigning them 70 total unforced errors to IDS’s 81 and my 84. Curiously, though, I found that Djokovic was far more successful on net forays than MSL did.

One thing all stat keepers agreed upon about the match was that it was messy — even 70 unforced errors are a lot for a two-set match. In his postmatch press conference, though, Federer disagreed, pointing out the subjective nature of the stats. “For me to miss a forehand after having three great reflex half-volleys from the baseline, to eventually miss a shot where you’re a little bit under pressure — it’s called an unforced error,” he said. “Look, for me, that is not worth the debate.”

Adding to the confusion, neither the IDS nor MSL numbers are available to the public online — though subscribers to tennistv.com can access the MSL numbers — nor will they be included in any record books. Winners, unforced errors and net points played and won all are unofficial stats. Instead they generally are used by broadcasters, reporters and scoreboard operators to shed light on matches — how they were played and won. No one scores many matches on the men’s and women’s tour, and even some matches at the Grand Slam tournaments, which get just the basic stats instead: first-serve percentage, winning percentage on first- and second-serve points, and the like. Chair umpires generate those stats automatically with their entries on consoles. They have severe limitations: They say nothing about which players was more aggressive, which played primarily from the baseline and which rushed the net, and how effective each player was from the forehand and backhand side. (And sometimes the tour gets these wrong, too: Before the final, the scoreboard showed the official serving and returning stats for Federer and Djokovic for 2012, with the players’ names reversed.)

But where they do exist, the counts of winners, unforced errors and net points come with downsides, too: They are highly subjective. If a player hits a big serve, approaches the net behind it but the return is out, is that a net point? The line between forced and unforced errors is especially fuzzy: At some tournaments, scorekeepers would tally an error off a hard-hit second serve as forced; at others, unforced. A winner should be the easiest to spot: a ball that’s in and the opponent doesn’t get a racket on before it bounces twice. But even there, some scorekeepers might count a shot as a winner if the other player gets just the tip of his racket on the ball.

These gray areas give rise to discrepancies between stats from different tournaments that employ different standards and scorekeepers. Players and journalists have grumbled many times, for instance, that Wimbledon scorekeepers are much more reluctant to hand out unforced errors than are French Open point loggers. Discrepancies such as those are common in sports: Baseball scorers in different ballparks may differ on what constitutes an error, and the same pass in one NBA arena might be scored as an assist while in another it isn’t. In the NFL, assigning tackles to players is highly subjective. Though some may disagree on those numbers, too, the official ones are accepted and used for player analysis.

What’s not common in sports is for two differing sets of the stats to exist side by side in the same arena. “Using the same vendor for in-stadium entertainment and the television feed is something we have looked at in the past and continue to evaluate,” said ATP spokeswoman Kate Gordon. “These are two distinct audiences we are talking to through different channels and systems, and you’ll find at many sporting events that in-stadium entertainment has subtle differences to what is appearing on world television feeds. The intent is certainly not to confuse anyone, but rather to provide entertainment and information to help make the match more interesting as people watch, wherever they are.”

Gordon added, “While all official statistics are consistent between the two, there can sometimes be differences in unofficial stats like winners and unforced errors, as they are judged subjectively and not kept as official records.”

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